Steering wheel suspension system

ABSTRACT

A method and a steering wheel suspension system for reducing the extent of injuries sustained by a driver in the event of a head-on collision of a vehicle that includes a steering wheel fitted with an air bag and having a steering shaft ( 8 ) which is rotatably carried in a holder device for steering purposes, wherewith the holder device is, in turn, mounted for rotation about a support shaft ( 2 ) which is based from the steering shaft and extends across the vehicle and, under normal conditions, is locked in a determined position relative to the support shaft ( 2 ) by means of a breakable locking device ( 14 ). The system includes a collision-initiated drive mechanism located at a radial distance from the support shaft ( 2 ) and functioning to apply to the holder device a force which causes the device to swing about the support shaft ( 2 ) and bring the steering wheel shaft to a generally horizontal collision position in front of the driver, wherewith the steering wheel ring is brought to a generally vertical position in front of the driver of the vehicle.

BACKGROUND OF THE INVENTION

The present invention relates to a method and to a system for reducingthe risk of injury to the driver of a vehicle in the event of a head-oncollision.

Essentially all cars are currently provided with steering wheelaccommodated air bags with the intention of preventing injury to thedriver.

However, an air bag is not able to absorb on its own the amount ofenergy required to arrest movement of an unbelted driver in the event ofa head-on collision of, e.g., 50 km per hour. The air bag is intended todistribute the load uniformly over the head and chest of the driver, sothat no part of the body will be subjected to local heavy loads. A majorpart of the kinetic energy concerned is normally absorbed in thesteering wheel suspension. Vehicles fitted with air bags therefore havesome form of collapsible steering wheel suspension, which is intended tocollapse in a controlled manner so as not to exceed a chest accelerationlimit of about 60 G.

In addition to being fitted with air bags, a number of vehicle modelsare also fitted with a so-called knee-bar structure. The knee-barstructure is intended to lessen the effects of hitting the underside ofthe instrument panel in the event of a head-on collision, and to absorbthe kinetic energy of the lower part of the driver's body. The knee-baris constructed so that the forces to which the driver's thighs aresubjected will not exceed about 10 kN. The knee-bar is normally placedinwardly of the instrument panel or dashboard frame and is not thereforevisible, said knee-bar normally being anchored in the vicinity of thesteering wheel suspension.

The course of events that occur when the vehicle hits a barrier or isinvolved in a head-on collision can be described in the following way:When a vehicle hits a barrier, the front part of the vehicle will bedeformed. The vehicle speed decreases at the same time as the drivercontinues to move essentially at the original, vehicle speed, causingthe driver to gradually approach and finally reach the forwardly lyingfurnishings, i.e. the steering wheel suspension, steering wheel, airbag, and knee-bar. These components shall be dimensioned for controlleddeformation, so as not to exceed the tolerance levels of the human body.

The characteristic that corresponds to front deformation of a vehicle isreferred to in the art as the pulse of the vehicle. The pulse alsodescribes the course of vehicle retardation during the collision. Anaggressive pulse, i.e. a rigid front-part, results in marked retardationof the vehicle. A quiet, or peaceful, pulse, i.e. a soft front-part thathas a long deformation distance, results in more gentle retardation. Aquiet pulse is, of course, preferable with respect to those travellingin the vehicle, but results in a larger vehicle.

The worst collision sequence on the part of the driver is when thevehicle has stopped completely before the driver has begun to load thefurnishings. This places a very high demand on the ability of thefurnishing to absorb the kinetic energy of the driver. An optimal courseof events can thus be described as one in which the driver is positionedso close to the furnishings as to load said furnishings initially priorto the crash or collision. The driver is then a part of the living massof the vehicle and can thus avail himself/herself of the deformationzone of the front part of the vehicle as an extended braking distance,which reduces the loads.

A driver will be seated at roughly the same distance from the frontfurnishings irrespective of the size of the vehicle and consequentlymuch greater demands are placed on the air bag system of a small car.Enhanced safety can be achieved by coupling or uniting the driver withthe car as quickly as possible in the event of a collision, so as tolimit the level of injuries sustained. Among other things, this requiresa stable steering wheel suspension, so that a reaction force can bequickly built-up. When the steering suspension is too soft, it is ableto deform without absorbing energy during the critical phase in whichdeformation of the car or vehicle is still in process. Another way ofrapidly coupling the driver to the car is to use highly aggressive andhard air bags that will be inflated quickly and therewith quickly couplethe driver to the car.

The majority of steering wheel suspension systems have a common mode ofbehaviour which dramatically influences the function of the system in avirtual traffic environment.

When an unbelted driver reaches the front furnishings during acollision, it is the driver's knees that first come into contact withsaid furnishings, due to the fact that the driver's knees are usuallythose parts of his/her body that are located closest to the furnishings.When the knees exert force on the knee-bar, the bar forces up thesteering wheel suspension, which, in turn, means that the steering wheelis pressed angularly upwards and away from the driver's chest. When thedriver then loads the air bag, the driver and the steering wheel willhave assumed a highly unfavourable angle, causing the driver to load thelower part of the steering wheel in the absence of any appreciable partof the air bag between him and the steering wheel. This phenomenon hastwo negative effects. Contact of the driver with the air bag results inthat the pulse can no longer be utilized and in the steering wheeltaking an unfavourable angle in relation to the driver's body. Thiseffect is currently compensated for by making the air bag larger andmore aggressive.

This problem has been observed in American studies on accidentsinvolving cars equipped with air bags. Head injuries are reduced whereasbreast injuries caused by the lower part of the steering wheel dominate.

Three parallel conditions have been tested in other tests, an unbelteddriver with air bag, three-point safety harness and air bag, and solelya lap belt and air bag. The results showed that the best combination isthe lap-belt and crash-bag combination, which resulted in the leastinjuries. The combination that includes a three-point harness is toorigid, since the air bag is optimised in respect of an unbelted driver.When solely a lap belt is used, the knees are unable to press forwardthe conventional steering wheel suspension and angle the steering wheelupwards, wherewith the hip-belt and crash-bag combination functions bestdue to this fact. The trials also showed that current air bags are notat all optimised towards a person wearing a three-point belt.

Another problem that occurs when the steering wheel suspension and thesteering wheel are angled upwards is that the ability of the steeringwheel suspension to absorb kinetic energy diminishes. The regulatedcollapse of the steering wheel suspension in the direction of carmovement is influenced by the application of further deformation.

The problems associated with current steering wheel suspensions can besummarised as follows:

Impact of the knees with the knee-bar causes the steering wheel to beangled upwards, therewith limiting the protection afforded by the airbag in the lower part of the steering wheel. The steering wheelsuspension must be strengthened, which increases both costs and weight.The absorption of energy offered by the steering wheel suspension in anaxial direction has a limited effect, since as a result of this anglingof the steering wheel the actual load does not act axially. Currentcrash-bag systems are optimised with respect to unbelted drivers. Theair bags are often overdimensioned.

The introduction of fewer movable parts and therewith limitation of thesteering wheel adjustment facilities is liable to result in the steeringwheel moving further away from the driver and its upward angle reduced.It is therefore normal for current day steering wheel suspension systemsintended for steering wheels that incorporate an air bag to lackadjustment facilities.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome the aforesaiddrawbacks.

This object is achieved with a steering wheel suspension method andsteering wheel suspension system of the kind that are characterized bythe features set forth in the claims.

Further features of the invention and advantages afforded thereby willbe evident from the following detailed description of a preferredembodiment of the invention, this embodiment being described by way ofexample only and having no limiting effect on the scope of theinvention. To facilitate an understanding of the following description,the text includes references to the accompanying drawings, wherewithequivalent or similar parts have been identified with the same referencesign.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, perspective view of one embodiment of the presentinvention.

FIG. 2 is a partially broken side-view of the system shown in FIG. 1.

FIG. 3 is a front view of the system illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic illustration of one embodiment of an inventivesteering suspension system. The system is described with reference to anautomobile (not shown) and is suspended from a steering wheel bar 1 thatextends beneath the dashboard between the so-called A-posts of theautomobile, these posts forming an attachment means for vehicle doorsand windows.

The steering wheel suspension system includes a steering wheel that isprovided with an air bag, and a steering wheel shaft 8 which isconnected to the vehicle steering mechanism and pivotally supported in aholder device for steering purposes. The holder device is, in turn,mounted for rotation about a support shaft which extends transversely ofthe vehicle and which, under normal conditions, is locked in a specificstarting position relative to the support shaft with the aid of abreakable locking means. Connected to the holder device is a drive meanswhich in the event of a head-on collision functions to deliver to theholding device a force sufficient to overcome the locked state of thelocking means and to swing the holder device in a direction which bringsthe steering shaft to a generally horizontal position and therewithbring the steeringwheel ring to a generally vertical position in frontof the driver of the vehicle.

The holding device of the illustrated embodiment is provided with meansfor adjusting the vertical and depth positions of the steering wheelshaft, and therewith also the steering wheel, according to the driver'spreference, when the holding device is located in its starting position.

A generally U-shaped tubular steering wheel suspension element 2 isfixedly fitted at its ends to the steering wheel bar 1, e.g. weldedthereto. In the illustrated embodiment, the tubular steering wheelsuspension element 2 includes the support shaft 2 around which theholder device pivots.

In the illustrated embodiment, the holder device includes a joint means7 which supports the steering wheel shaft and which is pivotally mountedon the tubular steering wheel suspension element 2.

The steering wheel shaft 8 is pivotally mounted in a slide sleeve 9which, in turn, can be moved axially in a tubular element 10 fixedlyconnected to the joint means 7. Provided on the underside of the slidesleeve is a row of teeth 7.2 which are intended to be placed inengagement with a complementarily designed adjustment mechanism.

In the illustrated case, the joint means 7 includes a U-bent plate jointhaving rotationally-stiffened plate bends, the free ends of said jointmeans being carried pivotally by the tubular steering wheel suspensionelement 2. A row of teeth 7.1 intended for engagement with acomplementarily designed adjustment mechanism is provided at respectiveouter edges of the joint means 7, in the proximity of the pivotalattachment.

The tubular steering wheel suspension element 2 also carries two deviceswhich are individually pivotal about said element, these devices havingthe form of a motor housing 3.1 and a motor housing 3.2, one on eachside of the joint means 7. Each of these motor housings houses arespective electric motor 5 and 6 whose output shafts are provided witha pinion wheel.

The upper part of the holder device thus includes the joint means 7, andthe lower part of said device includes the motor housings.

A cogwheel 4 provided with an external ring of teeth is mounted on thetubular steering wheel suspension element 2 between the motor housings3.1 and 3.2 and internally of the U-shaped joint means 7. The cogwheel 4has a diameter that permits engagement with the row of teeth 7.2 on theslide sleeve.

In the illustrated embodiment, a drive means is connected to the holderdevice such that in the event of a collision, the holder device will becaused to bring the steering wheel shaft to a collision position. In theillustrated embodiment, a movable knee-bar 12 is connected to the motorhousings 3.1, 3.2 and when subjected to the force of the driver's kneesfunctions to transfer these forces to the pivotally mounted motorhousings. The knee-bar is connected to the housings while spaced axiallyfrom the rotary axis of said housings—the support shaft —by means 13,such as to generate torque in the holder device.

The knee-bar 12 comprises a tubular element which is pivotally mountedat the steering wheel bar 1 and on which there is mounted a downwardlyhanging plate, which may be located between the steering wheelsuspension and the dashboard or instrument panel, or may constitute apart of the dashboard, for instance.

There is preferably provided between the motor housings 3 and theknee-bar 12 an energy-absorbing link 13 which is adapted to deform whensubjected to a specific load and therewith limit the collision violenceto which the driver's knees and hips are subjected. Such deformation,however, will preferably not occur until the holder device has beenrotated to its collision position.

Both electric motors 5 and 6 are fixedly mounted in respective motorhousings. The motor housings are suspended from the tubular steeringwheel suspension element 2 and when in a starting position are preventedfrom rotating about the tubular element 2 by means of rotationpreventing means 14 which will not release the motor housing forrotation until subjected to a load that exceeds a specified level. Therotation preventing means may have the form of shear pins, spring-biasedball locks, hooks which yield when subjected to loads that exceed aspecific level, or other means known to the person skilled in this art.

In normal driving conditions, the steering wheel suspension system willfunction in the same way as any other steering wheel suspension system,preferably with the advantage of providing two smooth steering wheeladjustment possibilities. The system enables the steering wheel to beadjusted depth-wise, i.e. the steering wheel may be moved towards andaway from the driver for adjustment purposes. The steering wheel canalso be tilted upwards and downwards, to a position in which the driverfeels comfortable at the wheel.

As will be evident from FIG. 2, the steering wheel is adjusteddepth-wise by regulating the electric motor 6, whose pinion wheel 6.1engages and rotates the cogwheel 4. When the cogwheel 4 rotates, therack 7.2 is actuated to move the slide sleeve 9 either forwards orbackwards, depending on the direction in which the cogwheel 4 is rotatedby the electric motor 6. The steering wheel shaft 8 on which thesteering wheel is mounted is fixed against movement axially in the slidesleeve but is mounted on bearings so as to be rotatable in said sleeve.The steering wheel shaft will thus accompany the slide sleeve 9 when itmoves in an axial direction.

As will be evident from FIGS. 2 and 3, the tilting movement is effectedby the cogwheels 5.1 of the electric motor 5 actuating the toothed rings7.1 of the joint means. Movement of the electric motor 5 causes thejoint means 7 to pivot about the tubular steering wheel suspensionelement 2, therewith causing the angle of the steering wheel shaft andthe steering wheel to change in accordance with the direction in whichthe cogwheels are rotated by the electric motor.

When no adjustment is made to the steering wheel setting, the shafts ofthe two electric motors 5 and 6 will be locked, and therewith preventrotation of the motors and the cogwheels mounted on their respectiveoutput shafts. The adjustment mechanism is fixed internally.

The following situation occurs in the event of a collision. As thevehicle begins to slow down, the driver's body continues to move forwardin the vehicle as a result of the mass inertia. The driver's knees,which are found relatively close to the furnishings, i.e. dashboard,etc., strike the knee-bar 12 carried by the steering wheel bar 1. Theknee-bar 12 is therewith pushed forwards towards and against the motorhousings. The energy absorbent 13 transfers this force between theknee-bar and the motor housings 3.1, 3.2 to the motor housings, whichare therewith subjected to an equally as large force as the knee bar 12.The energy absorbent transfers the whole of this force without itselfbeing deformed at this stage. When the load on the motor housing issufficiently large, the shear pins or like devices holding the motorhousings shear and the motor housings are rotated around the tubularsteering wheel suspension element 2.

When the holder device has reached its end position, has taken thecollision position, and the load on the knee-bar increases, the energyabsorbent in the knee-bar will begin to deform and therewith limit theloading forces exerted by the driver's thighs.

By making the motor housings individually pivotal, they can be caused toswing to different extents around the pivot shaft 2, by suitable leverselections. The choice of distance between the pivot shaft and the rowof teeth, or rack, 7.2 and the steering wheel shaft attachment at thejoint means will enable relative regulation of different pivotal andlinear-movement transmissions in the holder device. This enables, e.g.with locked motor shafts, the steering wheel shaft 8 to be moved axiallytowards the driver under the influence of the cogwheel 4 and,indirectly, of the locked cogwheel 6.1, as the holder device takes itscollision position.

It is beneficial to achieve some form of energy absorption in thesteering wheel suspension, when the driver's thorax exerts load on theair bag and therewith also the steering wheel suspension. This can beachieved, for instance, by allowing the steering wheel shaft to bepressed into the slide sleeve and deform the sleeve. Alternatively, thecogs on the slide sleeve may be allowed to deform against the cogwheel.Other arrangements for axially acting kinetic energy absorption known tothe skilled person may also be applied.

There is thus provided a steering wheel suspension which in the event ofa collision tilts the steering wheel shaft to a generally horizontalposition in which the steering wheel and steering wheel shaft arepositioned advantageously in front of the driver and therewith able toreceive the driver and brake his/her movement.

As a result of the horizontal position of the steering wheel shaft, notupwards, the steering wheel will be moved against the driver and broken,and hence the air bag will come into contact with the driver at a veryearly stage of the collision sequence and the collapse of the steeringwheel suspension can be dimensioned more readily.

Although the knee-bar 12 is preferably a one-piece structure, it mayalternatively be divided into two or more individually movable parts.The knee-bar, or knee-bars, may also include an aperture or slots whichwill allow the steering wheel shaft 8 to swing freely. This slot mayaccommodate a slide bearing 11 or some other means that contributestowards guiding and/or stabilising the steering wheel shaft.

Although the embodiment described above includes electricallyregulatable adjustment or setting facilities, it will be understood thatin other embodiments of the invention the electric motors may bereplaced with lockable, non-driven shafts that carry cogwheels. Whenthese shafts are in a free state, the driver is able to adjust the depthand height positions of the steering wheel manually, and to lock theshafts against rotation with the aid of appropriate means when thesteering wheel has been adjusted to a preferred position. Such anarrangement provides corresponding adjustment facilities even thoughthese facilities are implemented manually. In another embodiment, theholder device may lack completely any adjustment facility.

For instance, the holder device can be caused to take a collisionposition by an explosive charge which is triggered in a manner similarto that with current air bags, or in some other way by means which inthe event of a collision subject the holder device to a forcesufficiently high for the holder device to take a collision position.

The system may also be provided with locking means which, when thesteering wheel shaft has taken a collision position, functions to lockthe steering wheel shaft in said collision position, e.g. by means of ahook device provided to this end.

The steering wheel suspension system may be provided with a holderdevice that is pivotal solely in one range, the end position of whichconstitutes said collision position.

In another embodiment, the steering wheel suspension system may includethe suspension of pedals that can pivot around, e.g., the tubularsteering wheel suspension element 2. The pedal suspension may beconstructed in a manner such that when heavily pressed by the driver inthe event of a collision results in a similar sequence of events inwhich, e.g., shear pins or like power or force monitoring device areable to trigger corresponding pivotal movement of the holder device.

What is claimed is:
 1. A method of reducing the extent of injuriessuffered by a driver in the event of a head-on collision of a vehicleincluding a steering wheel which is fitted with an air bag and which hasa steering wheel shaft that is rotatably carried in a holder device forsteering purposes, said holder device being, in turn, mounted forpivotal movement about a support shaft which is spaced from the steeringwheel shaft and extends transversely in the vehicle and which undernormal conditions is locked in a determined position relative to saidsupport shaft by means of breakable locking means, the method comprisingthe steps of applying, at said head-on collision, a force at an impactsurface arranged in the vicinity of the vehicle dashboard and connectedto the holder device, therewith causing said holder device to swingabout the support shaft and bring the steering wheel shaft to anessentially horizontal collision position in front of the driver,wherewith the steering wheel will be adjusted to a generally verticalposition in front of the driver of the vehicle.
 2. A method according toclaim 1, wherein the steering wheel shaft is moved axially towards andagainst the driver when taking its collision position.
 3. A steeringwheel suspension system for a vehicle, the steering wheel suspensionsystem comprising: a steering wheel assembly with a steering wheel shaftcarried in a holder device that is pivotally carried by a support shaftand that is locked in a determined position by a breakable lock; and amovable impact surface that is connected to said holder device andspaced from said support shaft and that breaks said breakable lock uponapplication of a force to said impact surface to pivotally move saidsteering wheel shaft through an arc to a generally horizontal position.4. A system according to claim 3, wherein an energy-absorbing connectionpart is arranged between the impact surface and the holder device; andwherein the energy-absorbent part is dimensioned to absorb energy solelyin the event of a load that exceeds the force required to break saidbreakable lock and therewith release the holding device.
 5. A systemaccording to claim 3, wherein the holder device has two parts that canswing about the support shaft freely from one another, an upper part anda lower part; in that an angle locking device connects said upper andlower part for regulating their relative angular positions; and in thatan axial regulating device is arranged in said upper part for receivingand adjusting the steering wheel shaft in an axial direction.
 6. Asystem according to claim 3, wherein an energy-absorbing connection partis arranged between the impact surface and the holder device; andwherein the energy-absorbent part is dimensioned to absorb energy solelyin the event of a load that exceeds the force required to break saidbreakable lock and therewith release the holding device.
 7. A steeringwheel suspension system for a vehicle, the steering wheel suspensionsystem comprising: a steering wheel assembly with a steering wheel shaftcarried in a holder device that is pivotally carried by a support shaftand that is locked in a determined position by a breakable lock, saidholder device comprising two parts that are separately pivotable aboutsaid support shaft; an angle locking device that connects said two partsand regulates their relative angular positions; an axial regulatingdevice in one of said two parts that adjusts said steering wheel shaftin an axial direction; and a movable impact surface that is connected tosaid holder device and that breaks said breakable lock upon applicationof a force to said impact surface to pivotally move said steering wheelshaft through an arc to a generally horizontal position.
 8. A systemaccording to claim 7, wherein the steering wheel shaft is mounted in aslide sleeve and is fixed against axial movement in said sleeve butrotatable therein, said sleeve being accommodated in and axially movablein one of said two parts; wherein an underside of the slide sleeveincludes a row of teeth; wherein a cogwheel is provided for engagementwith said row of teeth; wherein the cogwheel is mounted for rotationabout the support shaft; and wherein an adjustable cogwheel is providedfor engagement with the cogwheel for axial adjustment of the steeringwheel shaft.
 9. A system according to claim 7, wherein the steeringwheel shaft is mounted in a slide sleeve and is fixed against axialmovement in said sleeve but rotatable therein, said sleeve beingaccommodated in and axially movable in one of said two parts; wherein anunderside of the slide sleeve includes a row of teeth; wherein acogwheel is provided for engagement with said row of teeth; wherein thecogwheel is mounted for rotation about the support shaft; and wherein anadjustable cogwheel is provided for engagement with the cogwheel foraxial adjustment of the steering wheel shaft.
 10. A system according toclaim 7, wherein an energy-absorbing connection part is arranged betweenthe impact surface and the holder device; and wherein theenergy-absorbent part is dimensioned to absorb energy solely in theevent of a load that exceeds the force required to break said breakablelock and therewith release the holding device.